The present invention relates to a drive unit for a movable part of a vehicle, such as a closure of an open roof construction.
Such drive units are known in various embodiments. An emergency clutch is normally used if the electric motor does not function anymore, for example if there is no voltage. In most embodiments it is necessary to use a tool, such as a screw driver, which must be inserted into the emergency clutch in order to rotate the axis of the motor and thereby the movable part of the vehicle.
If the drive unit is used in combination with a computer control unit, it is important for the control unit to know the position of the movable part. Normally, this position is measured by one or more electronic counters. If the movable part is manually adjusted through the emergency clutch, the actual position of the movable part will be different from the position stored in the memory of the control unit. This can lead to failures in the operation of the movable part.
There thus is a need to provide a drive unit with which this drawback can be removed.
According to an aspect of the invention, a drive unit includes an electric motor having a drive shaft and a transmission. An electric circuit includes said motor and a controller to actuate the motor. An emergency clutch is coupled to at least one of the drive shaft and transmission and reachable to enable hand actuation of the movable part in case of an emergency. The emergency clutch is covered by a part of the electric circuit, which is arranged such that it must be disconnected to reach the clutch.
Because of the necessity to disconnect the electric circuit to reach the clutch, it is possible to observe the use of the clutch, either visibly, electronically or the like. Then, measures can be taken to ensure a correct operation of the movable part, for example by manually or automatically resetting the control unit, or by disabling certain functions of the control unit.
In one embodiment, part of the electronic circuit is provided on a breakable seal, such as a pierceable metal foil. From the condition of the seal it can always be deduced when the clutch has been used or reached, since the disruption is irreversible. Preferably, the seal is mounted such that an expert can very easily replace the electric seal.
If the part of the electric circuit is a detection circuit, the control unit will detect the disconnection in the electric circuit and can make a programmed decisions, for example to reset automatically or to disable certain functions.
Another aspect of the present invention also includes an open roof construction for a vehicle, such as a passenger car, comprising such drive unit.